Organic Chem Flashcards
Hydrocarbon
A compound containing hydrogen and carbon only
Homologous series
A group of compounds with the same functional group and similar chemical properties w successive members differing by CH2
Functional group
The part of the organic molecule largely responsible for the molecules chemical properties
Alkynes
Contain at least one triple c c bond
Branching on deciding longest chain length when 2 chains are the same length
Chain with most branches is considered longest
How are side chains ordered
Alphabetically
Ester suffix
-Oate
Molecular formula
Shows the number and type of atoms of each element present in a molecule
Empirical formula
The simplest whole number ratio of atoms of each element present in a compound
General formula
The simplest algebraic formula for any member of the homologous series
Structural isomers
Compounds with the same molecular formula but different structural formula
Similarities between aldehydes and ketones
Same molecular formula
Homolytic fission
When each of the bonded atoms takes one of the shared pair of electrons from the bond same molecules or same electronegativity
Heterolytic fission
When one of the bonded atoms takes both of the electrons from the bond more electronegative different atoms
What is an elimination reaction
A reaction involving the removal of the small molecule from larger one
Uses CH4 to C4H10
Gas in domestic fuel
C5H 12 to see C9H 20
Petrol in car is
C10 C16
Kerosene used an aircraft
C12 C20
Diesel used in cars and lorries
Trend in boiling point of alkanes
As chain length increases boiling point increases due to weak intermolecular forces London forces holding molecules together in solids and liquids
Effect of chain length on boiling point
London forces act between molecules in close the surface contact as the chain length increases molecules have a larger surface area so more service contact as possible so London forces will be greater and more energy is required to overcome the forces
Effect of branching on boiling point
Branched isomers have lower boiling points
Why does branching affect boiling point
Branched molecules mean fewer surface points of contact between molecules of branched alkanes giving fewer London forces branches get in the way and prevent the branch molecules getting as close as straight-chain
Why are alkanes not reactive
Sigma bonds are strong carbon carbon bonds are nonpolar carbon hydrogen bonds are nonpolar
Why are alkanes used as fuels
They are readily available easy to transport and burn and oxygen without releasing toxic products
What are the conditions are an alkane to react with the halogen
UV radiation or sunlight
Three stages of radical substitution
Initiation propagation termination
Limitations of radical substitutions
Further substitution CH3Br+Br2——>CH2Br2+HBr
Until all hydrogens have been substituted
Substitution at different positions in a carbon chain forming many isomers
Carbon bonds in an alkene
Each carbon has three of the four outershell electrons bonded in three Sigma bonds one to another carbon and 2 to 2 other atoms one electron on each carbon atom of the double bond is in a P orbital
What are Pi bonds
The adjacent overlap of 2p orbitals one from each carbon atom of the double bond the pi electron density is concentrated above and below the line joining the nuclei of the bonding atoms the double bond locks the carbon is in position and prevents rotation
Stereoisomers
Have the same structural formula but a different arrangement of atoms in space
Where does EZ isomerism occur
Only in compounds with a carbon carbon double bond
Why does stereoisomerism occur
Because rotation around the double bond is restricted due to the pipe on electron density above and below the plane of the sigma bond
CIs trans isomerism
A special case of EZ isomerism where two of the bond groups are hydrogen
Cis
Z
Assigning priority
The higher the atomic number the higher the priority
Why are alkenes more reactive than alkanes
The presence of the pie blonde the pi bond electron density is above and below the plane of the Sigma bond being on the outside of the double bond the Pi electrons are more exposed and break readily undergoing addition reactions easily
Condition of the hydrogenation of alkenes
Nickel catalyst 423K
Addition reactions of alkenes
Hydrogen in the presence of a nickel catalyst
halogens
hydrogen halides and
steam in the presence of an acid catalyst
Conditions for the halogenation of alkenes
Room temperature bromine water added to an alkene the double bond breaks and the orange solution goes colourless
(Test for alkenes)
Addition reaction of hydrogen halides
Room temperature if the alkane is a gas reaction takes place were to gases are mixed if the alkene is a liquid The hydrogen halide is bubble through it also react with concentrated hydrochloric acid which are solutions of hydrogen halide in water
Room temp
Hydration reaction of alkenes
Form alcohols in a reaction with steam H2O (g) in the presence of a phosphoric acid catalyst H3PO4
Electrophile
Electron pair acceptor
Nucleophile
Electron pair donator
What causes polarisation of Br2 in the electrophilic addition of alkenes
Reaction between the bromines electrons in the pie bond electrons repelled
Primary products
Atom attached to a carbon attached to 2 hydrogen atoms
Secondary products
Atom attached to a carbon attached to one hydrogen atom
Tertiary product
Atom attached to a carbon not attached to any hydrogens
How are carbocations classified
By the number of alkyl groups attached to the positively charged carbon atom
Which carbocation is most stable
Stability increases with the number of alkyl groups
Stability is linked to the electron donating ability of alkyl groups each alkyl group donates electrons towards a positive charge so the positive charge is spread over a larger area
Repeat unit
Specific arrangement of atoms in the polymer molecule the repeats over and over always written in square brackets
Condition from addition polymers
Heating a large number of monomers at high-pressure and temperature
Polychloroethane
C2H3Cl
Used in pipes insulating cables flooring and bottles
Polypropylene
Used in children’s toys
Polystyrene
Packaging material
Tetrafluoroethylene
Coating for non-stick pans
Why is it hard to dispose of waste polymers
Non-biodegradable and unreactive
Recycling polymers
Conserve is finite fossil fuels and decreases the amount of waste going to landfill have to be sorted by type cannot be mixed recycled polymer is cut into pellets and used by manufacturers to make new product
PVC recycling
PVC has it is due to high chlorine content not sustainable to dump it when burnt PVC releases hydrogen chloride which is a corrosive gas
Uses of waste polymers
As fuel can be burnt to produce heat generating steam to drive a turbine producing electricity
Feedstock recycling is grades chemical and thermal processes that can reply monomers from waste polymers monomers can then be used to produce new polymers
Sustainable ways of disposing of waste polymers
Bio plastics alternative which is renewable and sustainable products based of plant starch Celulose and oils
Biodegradable polymers broken down by microorganisms into water carbon dioxide and biological compounds
Photodegradable polymers oil based polymers that are photodegradable contain bonds that r weekend by absorbing sunlight to start degradation or light absorbing additives
Comparing alcohols and alkanes
Alcohols a less volatile have higher melting points and greater water solubility
Why are alcohols less volatile than alkanes
Alcohol is a polar alkanes are nonpolar intermolecular forces between nonpolar molecules a week London forces alcohols form permanent dipoles and stronger hydrogen bonds. Which requires more energy to turn into a gas and break bonds than alkanes
Solubility
Alcohols can form hydrogen bonds with water says much more water soluble alkanes are not polar and can’t form hydrogen bonds
Solubility with increasing carbon chain of alcohol is
Decreases as the influence of the OH group becomes smaller and solubility of long chain alcohols become more like hydrocarbons
Combustion of alcohols
Form carbon dioxide and water in an exothermic reaction
Oxidation of alcohols condition
Primary and secondary alcohols a mixture of potassium dichromate acidified with dilutes sulfuric acid
Colour changing and oxidation reaction
Cr2O7 2- ——> Cr 3+
Colour change from Orange to green
Forming in aldehyde
Distillation of primary alcohol
Preparation of carboxylic acid
Primary alcohol heating on the reflux with excess of acidified potassium dichromate
Oxidation of secondary alcohols
Oxidised to ketones on the reflux
Oxidation of tertiary alcohols
Do not undergo oxidation reactions
Dehydration of alcohols
Water molecule removed
Alcohol heated on the reflux in the presence of an acid Catalyst
H3PO4 or H2SO4
Elimination reaction
Substitution of reactions of alcohol is
Occurs with hydrogen halides to form halo alkanes alcohol heated under reflux with sulphuric acid and sodium halide hydrogen bromide is formed then the hydrogen bromide reacts with alcohol to form the halo alkane and water
Substitution in haloalkanes
Nucleophilic substitution
How can halo alkanes be converted to alcohols
Using aqueous sodium hydroxide slow at room temperature so heated under reflux
Rate of hydrolysis in haloalkanes
Depends on the carbon halogen bond strength carbon fluorine bond is strongest Corbin iodine bond is the weakest less energy required to break so Iodo alkanes react faster
Measuring the rate of hydrolysis
Add ethanal and silver nitrate and wait for precipitate to form
Hydration of primary secondary and tertiary haloalkanes
Tertiary halo alkane hydrolysed fastest primary slowest primary haloalkane reacts by one step mechanism whereas secondary reacts w two step mechanism
Alternatives to CFCs
Brominated flame retardant organic bromine
What happens when organic compounds place in the mass spectrometer
It loses an electron and forms a positive ion the molecular Ion the mass spectrometer detects the mass to charge ratio of the molecular ion which gives the molecular mass
Identifying the number of carbon atoms in a mass spectrum
Height of m+1 peak/height of m peak x100
What does the amount a bond stretches or bends depend on
The mass of the atom heavier atoms vibrate slower than lighter the strength of the bond stronger bond vibrate faster than weaker bonds
What happens in an infrared spectrometer
Sample placed inside a beam of IR radiation is passed through the sample molecules absorb some IR frequency and the emerging beam of radiation is analyse to identify the frequencies that have been observed connected to the computer the plot a graph a transmittance against wavenumber
Application of infrared spectroscopy
Pollutants recognised and in breathalysers IR radiation passed through sample measures emissions and ethanol in the breath
Common solvents used in NMR spectroscopy
CDCl3
Still produces a peak in a carbon 13 spectrum but the computer usually filters out this peak
Carbon 13 NMR spec provides two pieces of information
The number of carbon environments and the type of carbon environment
Proton NMR gives four pieces of information
The number of proton environments the type of proton environments the number of protons each environment and the number of non-equivalent protons adjacent to a given proton
Proton exchange
Classifies 0H protons proton NMR is run then a small volume of deuterium oxide is added the mixtures shaken then second spectrum is run deuterium exchanges and replaces the OH and NH protons in the sample with deuterium atoms D does not absorb in this chemical shift range so the OH Peak disappears
Alternative is to CFC
HCFC HFC
Hydrocarbons
HCFCs broken down in 10 years smaller effect
But are greenhouse gases
Hydrocarbons in fridges
Aerosols replaced by pump sprays or use nitrogen
Ammonia in freezers and co2 to make foam polymers
Test for aldehydes
Tollens reagent
Silver mirror forms
